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The 46-year-old playboy was sprayed in the face with an unknown chemical by two women. One female suspect has been arrested by police.

Kim Jong Nam is seen in Macau, the former Portuguese colony

Now, investigators will be trying to piece together what led to Mr Kim's death, amid widespread speculation he was targeted by the North's current leader, Kim Jong-un.

Mr Kim was the older half-brother of the Supreme Leader, who reportedly lives in fear of being overthrown by his own family members.

Here are four things that may have sealed Mr Kim's fate as the latest person to be executed by the brutal North Korean regime.

Troubled relationship with original 'Supreme Leader'

Kim Jong-nam's uneasy relationship with the North Korean leadership started at birth.

The oldest son of Kim Jong-il, Kim Jong-nam was born in Pyongyang in May 1971.

Kim Jong-Nam dressed in an army uniform poses with his maternal grandmother in January 1975

His father, who would go on to rule North Korea from October 1997 until December 2011, initially tried to keep his son's existence secret from his own father, Kim Il-sung, who disapproved of his relationship with an actress.

That actress was Song Hye-rim, one of several actresses known to have been a mistress of Mr Kim's father.

The 'Disneyland' incident

Kim Jong-nam was once considered the heir apparent to Kim Jong-il, but fell out of favour in 2001 after being arrested at Tokyo's Narita Airport after trying to enter Japan on a forged Dominican Republic passport.

Detained and held for three days, he told immigration officials that he had wanted to visit Tokyo Disneyland.

The incident is likely to have caused significant embarrassment in Pyongyang and harmed an already fractured relationship between Mr Kim and the North Korean regime.

In his book "Under the Loving Care of the Fatherly Leader", Bradley Martin stated that Kim Jong-nam had been a visitor to Japan on numerous previous occasions and was a regular client in some of the bathhouses in the Yoshiwara red-light district of Tokyo.

An embarrassed Kim Jong-il cancelled a planned visit to China and Kim Jong-nam effectively went into exile in Macau, where he was apparently using a forged Portuguese passport to travel.

Botched assassination

One source told the Daily Mail in 2015 that North Korean spies attempted to kill Kim Jong-nam in Macau in 2011.

A bloody shootout with Mr Kim's bodyguards ensued, but he managed to escape with his life.

It is likely that the failed attempt only emboldened North Korea in its efforts to silence Mr Kim.

The 'begging letter'

Kim Jong-nam wrote to Kim Jong-un in 2012 asking his half-brother and the recently anointed dictator of North Korea to spare his life and that of his family, according to the head of South Korea's National Intelligence Service.

Lee Byong-ho, the director of the agency, told a meeting of the government's Intelligence Committee that Kim Jong-nam had been murdered with poison in Malaysia on Monday and that he had survived at least one previous attempt on his life, Yonhap News reported.

After that assassination attempt, in 2012, Kim Jong-nam wrote to his brother and asked that no further attacks be directed at him or his family. That plea clearly fell on deaf ears.